Magnetic and electrical performance of atomic layer deposited nanolaminates

The synthesis of multiferroic materials is of relevance while developing the next generation electronic and spintronic devices [1]. Theoretically, several materials could demonstrate saturating and remnant polarization in both... [ view full abstract ]

The synthesis of multiferroic materials is of relevance while developing the next generation electronic and spintronic devices [1]. Theoretically, several materials could demonstrate saturating and remnant polarization in both electric and magnetic fields, but it is challenging to actually synthesize thin films which demonstrate multiferroic behaviour, because the physical performance of the materials may considerably depend on their synthesis routes. In this study the nanolaminate films consisting of high-permittivity oxides (ZrO₂, Er₂O₃) and magnetic materials, (Fe₂O₃, Co₃O₄) were grown by atomic layer deposition (ALD) on silicon and titanium nitride substrates at 300, 350 and 375 °C using erbium diketonate, ferrocene, zirconium chloride, tris(2,4-pentanedionato)cobalt and ozone precursors. Laminated ALD films could be uniformly deposited into three dimensional stacked substrates using the same cycle times otherwise suited to the uniform coverage of planar substrates (Fig. 1 d). Morphology, crystalline phases and composition of Fe₂O₃-Er₂O₃ (Fig. 1), Co₃O₄-ZrO₂ (Fig. 2) and Fe₂O₃-ZrO₂ [2] stacked oxides were described. The multilayered structures promoted both charge polarization and saturative magnetisation compared to these phenomena in the more homogeneously mixed films (Fig. 1 d, e). Promising results in terms of the simultaneous appearance of the internal magnetization and certain electrical charge polarization were demonstrated in planar laminated structures. Further electrical and magnetic modelling and analysis will be needed in order to elaborate the phenomenon and optimize the material structure for the magnetoelectric performance.

Acknowledgements

This work was funded by the European Regional Development Fund the project TK134 “Emerging orders in quantum and nanomaterials”, Estonian Research Agency (IUT2-24), Estonian Academy of Sciences (SLTFYUPROF), and Spanish Ministry of Economy and Competitiveness through the project TEC2014-52152-C3-3-R with support of Feder funds.

References

[1] R. Thomas et. al., “Multiferroic thin-film integration onto semiconductor devices”, J. Phys. Condens. Matter, 2010.

[2] K.Kalam et. al., “Atomic layer deposition of ZrO₂-Fe₂O₃ thin films”, Beilstein J. Nanotechnol., 2017 submitted.